Polyamide thermoplastic elastomer obtained by blending

ABSTRACT

Novel thermoplastic elastomer compositions, made by dispersing a polyolefin elastomer phase containing functionalized EPM or EPDM in a polyamide resin followed by cross-linking of the elastomer phase, are described. The cross-linked phase exists as discreet particles, providing an overall blend which remains thermoplastic. The resulting blend may be used in the fabrication of elastomeric goods without the need for a separate vulcanization step after the desired object is formed.

This is a divisional of application Ser. No. 08/126,432 filed on Sep.24, 1993, now U.S. Pat. No. 5,397,835, which is a continuation ofapplication Ser. No. 07/625,874 filed on Dec. 11, 1990, now abandoned,which is a divisional of application Ser. No. 07/185,108 filed on Apr.22, 1988, issued as U.S. Pat. No. 5,003,003 on Mar. 26, 1991.

FIELD OF THE INVENTION

This invention relates to polyamide-hydrocarbon elastomer blends havingimproved physical and mechanical properties. More particularly, thisinvention relates to blended polyamide thermoplastic elastomers havingimproved tensile strength, elongation and oil resistance properties.

BACKGROUND OF THE INVENTION

Thermoplastic elastomers are typically materials which exhibitproperties intermediate between those of crystalline or glassy plasticsand soft rubbers. To be considered thermoplastic they must soften uponheating such that in the softened state they are capable of being shapedby flow into articles by molding or extrusion, and upon cooling theymust resolidify in order to maintain their molded or extruded shape.

Among the thermoplastic elastomers that have become commerciallyimportant a number are based upon physical blends of plastics andelastomers. Examples of these are described in U.S. Pat. Nos. 3,806,558,3,835,201, 3,957,919, 4,130,535 and 4,311,628, all of which teachcompositions which are comprised of polyolefin resins containing eitheruncured, partially cured, or fully cured polyolefin elastomers. Suchcompositions exhibit useful properties largely because of thecompatibility that exists between hydrocarbons of similar chemicalstructure. The above cited patents also teach that further improvementin physical properties such as tensile strength, elongation, and tensionset is realized when the elastomer phase is well dispersed into smallparticles of fixed size by virtue of curing the elastomer in itsdispersed state without curing the plastic so as to maintain itsthermoplasticity.

Thermoplastic polyamide resins and improvements in the physical andmechanical properties thereof have been made the subject matter ofresearch and development over a considerable period of time. Much ofsuch earlier reseach and development has been addressed to the admixtureof the polyamides with a variety of additives, including rubber-like orelastomeric materials, such as ethylene-propylene copolymers (EPM) orethylene-propylene polyene terpolymers (EPDM), and other modified andunmodified resins with various degrees of success. The desired level ofimprovement has not been achieved with the addition of such elastomericmaterials due primarily to the relative incompatibility between theelastomeric materials and the polyamide resins.

Attempts have been made to overcome this problem and increase thecompatibility between the hydrocarbon elastomeric materials and thepolar polyamide resins by modification of the elastomeric materials toprovide reactive sites that enable the polyamide resins to adhere to theelastomeric materials.

For example, blends of hydrocarbon rubbers in polyamide plastics aretaught in U.S. Pat. No. 4,594,386. In that patent the inherentincompatibility between the hydrocarbon rubber and the polar nylon isovercome by grafting the rubber with maleic anhydride, such thatcompatibility is achieved by reaction of the grafted anhydride groups onthe rubber with the amino end groups of the nylon. The '386 patent,however, addresses rigid nylon molding compositions having improvedimpact strength, rather than flexible thermoplastic elastomercompositions, and teaches that the elastomer level is limited to below50 percent. Furthermore, there is no teaching that additionalimprovement in the properties of the compositions may be obtained fromcross-linking of the dispersed rubber.

Thermoplastic elastomer compositions of a modified EPDM rubber and nylonare taught in U.S. Pat. No. 4,017,557. The compositions of that patent,however, are restricted to uncured blends of modified EPDM polymers withlow molecular weight nylons having a degree of polymerization of lessthan 60. The patent does not teach or suggest the benefit that might berealized from cross-linking the dispersed rubber particles, nor does itsuggest that useful properties might be achieved with typical commercialmolding and extrusion grade nylons having degrees of polymerization inthe range of 100-400.

U.S. Pat. No. 4,338,413 teaches thermoplastic elastomer compositionswhich are comprised of blends of polyolefin plastics containingdispersed fully cured particles of a hydrocarbon elastomer withpolyamide plastics containing dispersed fully cured particles of a polarelastomer. Compatibility is achieved through the addition of afunctionalized olefin polymer. The patent, however, does not teachcompositions in which the plastic component is taken from a single classof polymers, i.e., polyamides, nor does it teach polyamide thermoplasticelastomer compositions containing only hydrocarbon elastomers.

SUMMARY OF THE INVENTION

It has been found, in accordance with the practice of this invention,that marked improvement in tensile strength, elongation, and oilresistance of polyamide-hydrocarbon elastomer blends can be achieved bydispersing in the polyamide resin a functionalized hydrocarbon elastomerhaving amine reactive groups and, optionally, additionalnon-functionalized vulcanizable hydrocarbon elastomer, and thencross-linking the dispersed elastomer. The polyamide thermoplasticelastomer blends of this invention comprise from 10-70 percent by weightof the polyamide resin and from 30-90 percent by weight of theelastomer. The polyamides useful in the invention are typical commercialmolding and extrusion grade nylons having degrees of polymerization inthe range of 100-400.

There are a number of criteria which should be followed in order toachieve the desired results sought to be obtained by the practice ofthis invention. It is important that the functionalized hydrocarbonelastomer be sufficiently gel free prior to blending with the nylonresin to obtain a suitable dispersion of the rubber in the resin.Suitable methods for preparing grafted hydrocarbon elastomers having alow gel content are described in my co-pending applications U.S. Ser.No. 716,672, now allowed, and U.S. Ser. No. 858,890.

The functionalized hydrocarbon elastomer may be a chemically modifiedpolymer or a graft copolymer made by polymerizing a di-functionalmonomer having an amine reactive group in the presence of the basehydrocarbon polymer. Examples of the first type include EPDM polymerthat has been thermally adducted with maleic anhydride as described inU.S. Pat. No. 3,884,882, EPM or EPDM polymer that has been reacted withmercaptans or azides having amine reactive groups and EPM chemicallymodified with methylol phenol groups. Examples of the second type offunctionalized hydrocarbon elastomer include EPM or EPDM polymersgrafted with difunctional monomers having amine reactive groups such asmaleic anhydride and glycidyl methacrylate. These may be prepared eitherin solution or by bulk polymerization grafting in extruders or internalmixers.

The only, restriction placed upon the polyamide resin is that it containsufficient amine groups to react with the amine reactive groups on tilefunctionalized hydrocarbon rubber, thereby enhancing the compatibilitybetween the non-polar hydrocarbon rubber and the polar nylon plastic. Ingeneral the chemistry of polyamide synthesis is such that chains havingamine groups at either or both ends may be obtained. In the practice ofthis invention a resin of either type or a mixture thereof would beacceptable provided that the degree of reaction between the elastomerand the nylon does not reduce the thermoplasticity of the product to anunacceptable level.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term "Polyamide resin" includes all polymers havingrecurring carbonamide groups in the main chain, and having molecularweights greater than 2000, and preferably in the range of 10,000-40,000"Molecular weight" as used herein, refers to number average molecularweight for polyamides (see Flory Principles of Polymer Chemistry", page273, published 1953 by Cornell University Press). The preferredmolecular weight corresponds to degrees of polymerization in the rangeof 100-400.

The polyamide resin is ordinarily produced by condensation of equimolaramounts of dicarboxylic acid or acid derivative containing from two totwenty carbon atoms, with a diamine, containing from two to fifteencarbon atoms, or by lactam polymerization according to well knowntechniques. Preferred polyamides are those based on lactams and thosebased on aliphatic diamines condensed with aliphatic or aromaticdiacids. Included in this group are polyhexamethylene adipamide (nylon6.6), polycaprolactam (nylon 6), poly(undecaneamide) (nylon 11),poly(dodecaneamide)(nylon 12) polyhexamethylene sebacamide (nylon 6.10),polyhexamethylene isophthalamide, polyhexamethylenetereco-isophthalamide, and mixtures or copolymers thereof.

Polyamides of the type described have been marketed by AlliedCorporation under the trade name Capron, by E.I. dupont de NemoursCompany under the trade name Zytel, and by Rilsan Corporation under thedesignation BMNO. The resins are typically crystalline and high melting.The useful features of this invention, however, are not limited tocrystalline polyamides and may also apply to glassy amorphous polyamidessuch as the aramides marketed by Emser Industries, Inc. under the tradename Grilamid.

Suitable base hydrocarbon elastomers of the instant invention arecopolymers of ethylene, an alpha-olefin, and optionally a non-conjugateddiene. Examples of such hydrocarbon elastomers are those marketed byCopolymer Rubber and Chemical Corporation under the tradename EPsyn andthose marketed by E.I. dupont de Nemours and Company under the tradenameNordel. Persons familiar with the art will recognize that the techniquesof this invention are general enough to be applied to compositions whichmake use of other, substantially hydrocarbon elastomers, especiallybutyl rubber, bromo or chlorobutyl rubbers, and styrene block copolymerswith butadiene and isoprene, especially the hydrogenated styrene blockcopolymers.

As the component grafted onto the EPM rubbery copolymer, it is preferredto make use of maleic anhydride but other unsaturated dicarboxylic acidanhydrides diacids, or mixed acid/esters may be used having the generalformula ##STR1## in which R is an alkylene group having from 0-4 carbonatoms and Y is preferably hydrogen but may be an organic group such as abranched or straight chain alkyl group, heterocyclic or other organicgroup of 1-12 carbon atoms, a halogen group such as chlorine, bromine,or iodine and in which at least one, and preferably both of the X groupsare hydroxyl but in which one of the X groups may be an alkoxy oraryloxy group having from 1-8 carbon atoms.

For example, the maleic anhydride in the following examples may besubstituted in whole or in part with equal molecular equivalents ofother unsaturated dicarboxylic acids or anhydrides, such as itaconicacid or anhydride, fumaric acid, maleic acid and the like.

The grafting reaction is carried out in the presence of a peroxidecatalyst such as dicumyl peroxide, t-butyl hydroperoxide, benzoylperoxide, t-butylperoctanoate, di-t-butylperoxide, t-butylhydroperoxide,cumene hydroperoxide, t-butylperbenzoate or other free radical sourcecapable of hydrogen abstraction, as represented by alkyl peroxy esters,alkyl peroxides, alkyl hydroperoxides, diacylperoxides and the like. Theamount of catalyst as well as reaction conditions will vary with thechoice of catalyst.

The desired results are achieved when the amount of anhydride or didcidgrafted onto the EPM polymer is within the range of 0.2-5 percent byweight of the base polymer and preferably in an amount within the rangeof 0.5-4 percent graft. In general, the amount grafted onto the polymerwill represent only 30-50 percent of the graft material reacted with thepolymer. For example, to achieve a graft of 4 percent maleic anhydrideonto a preformed EPM polymer, a charge of about 10 percent maleicanhydride will be required.

As the component grafted onto the EPDM polymer, it is preferred to makeuse of glycidyl methacrylate, although other epoxy compounds having thefollowing general formula may be used: ##STR2## in which R' is anorganic group having an epoxide functionality and R is hydrogen, methyl,ethyl, propyl or other alkyl, aralkyl, cyclic, or aromatic group.Representative of such other modifying agents are glycidyl acrylate,glycidyl 2-ethylacrylate, glycidyl 2-propylacrylate and the like.

The grafting reaction is carried out in the presence of a catalyst thatfavors grafting over a cross-linking reaction under the reactionconditions to combine the glycidyl methacrylate with the unsaturatedbackbone rubber. For this purpose, it is preferred to make use of a freeradical initiator such as a dialkyl peroxide. In the grafting reaction,use can be made of the catalyst in an amount within the range of 1-5parts per 100 parts by weight of the unsaturated rubber, and preferablyin an amount within the range of 1-2 percent by weight.

The level of the graft of the glycidyl methacrylate onto the unsaturatedbackbone rubber is somewhat dependent on the amount of unsaturation inthe backbone, rubber. It is desirable to make use of an ethylene,mono-olefin, polyene backbone rubber having at least two unsaturatedcarbon-to-carbon linkages per 1000 carbon atoms and little additionalbenefit is derived from the use of an unsaturated backbone rubber havingmore than 20 carbon-to-carbon double bonds per 1000 carbon atoms. In thepreferred practice of this invention, use is made of an unsaturatedrubber having from 4-10 carbon-to-carbon double bonds per 1000 carbonatoms or which provide for a level of graft within the range of 1-10percent and preferably 1.5-4 percent by weight of the rubber.

The grafting reaction may be carried out in solvent solution with theunsaturated rubber present in a concentration which may range from 10-30percent by weight, with constant stirring, at an elevated temperaturewithin the range of 125°-200° C. for a time ranging from 1/2-2 hours.The reaction condition can be varied depending somewhat upon the typeand amount of catalyst and temperature condition, as is well known tothe skilled in the art.

It is widely known that unmodified EPM and EPDM rubbers producenon-homogenous blends having no property enhancements when admixed withpolyamide resins. This is possibly because of incompatibility of the EPMand EPDM rubbers due to their inherent non-polar nature. On the otherhand, the functionalized elastomers described herein provide homogenousblends with polyamide resins which, after cross-linking of the dispersedelastomer, yield a product with significant improvement in tensilestrength and elongation.

The improved tensile strength and elongation properties are obtainedwith a blend of polyamide resin and functionalized hydrocarbon elastomerin the ratio of 30-90 percent by weight of the elastomer per 70-10percent by weight of the polyamide resin, and preferably in the ratio of40-90 percent by weight of the elastomer per 60-10 percent by weight ofthe polyamide resin.

Such blends are prepared using equipment that is suitable for blendingmolten polymers. This includes melt processing equipment such asBrabender and Banbury mixers, heated roll mills, extruders, and thelike. The mixing should be carried out at a temperature above themelting or softening point of the polyamide resin. Generally, the mixingis carried out at temperatures in the range of 190°-300° C. Addition ofany curatives should be withheld until the rubber and polyamide resinare suitably mixed. The curatives may be, for example, peroxide cures,such as those sold under the designation Varox, metal cures, such aszinc stearate, calcium stearate, zinc oxide or magnesium oxide, sulfuror sulfur donor cures, as well as phenolic resin cures, such as thoseused for curing butyl rubber. Use can also be made of excessfunctionality on the functionalized hydrocarbon. For example, maleicanhydride or glycidyl methacrylate functional elastomer might becross-linked by addition of compounds containing two or more amine,epoxide, alcohol or carboxylic acid groups. This amounts to crosslinkingvia chemical reaction of the amine reactive groups on the functionalizedhydrocarbon elastomer. The amount of curative will vary according to thetype of cure and the composition of the blend.. Other compoundingingredients such as oils, plasticizers, flame retardants, stabilizers,and fillers optionally may be added to further modify the finalproperties of the composition. Blending time should be long enough toachieve suitable dispersion of the components and long enough as well toachieve the desired degree of cure.

The teachings of the invention will now be illustrated by the followingexamples, which are in no way intended to be limiting.

Example 1 illustrates the preparation of an amine reactive hydrocarbonelastomer.

EXAMPLE 1

The starting polymer is an amorphous ethylene/propylene rubber having 55mole percent ethylene, 1.92 RSV as measured on a 0.1% solution indecalin at 135° C., and a Mooney viscosity of ML (1+4) 20 at 257° F. Themelt flow index of the starting rubber was found to be 2.5 g/10 minutesunder Condition L of ASTM D1238.

A 17.1 weight percent solution of the starting rubber (29.1 kg) in dryhexane was heated to 156° C. in a sealed, agitated 80-gallon stainlesssteel reactor. Maleic anhydride (1998 g) in 11.4 liters toluene waspressured into the reactor. After allowing for mixing of the monomer,436 g dicumyl peroxide (Hercules Di-Cup T) in 1.9 liters hexane waspressured into the reactor. The temperature and pressure were held at156°-158° C. and 126-138 psig, respectively, for 60 minutes. Aftercooling of the mixture, the product was steam coagulated and dried at65°-80° C. before use. Tritrimetric analysis of a purified sampleindicated 1.7 weight percent bound maleic anhydride.

Examples 2-8 illustrate thermoplastic polyamide elastomer (TPE)compositions of the instant invention.

Procedure

The mixtures were prepared in a Brabender U Plasticorder mixing headoperating at 75 RPM using the cam rotors. Operating temperature was 195°C. in the case of Nylon 11 mixtures and 230°-240° C. in the case ofNylon 6 mixtures. In a typical procedure the rubber and resin were mixedfor three minutes after the resin melted; then the curatives were added.Curing of the rubber was evidenced by an increase in torque as noted onthe Brabender chart recorder. Mixing was continued for five minutesafter the last ingredient was added. The batch was dumped, cut intosmall pieces, and remixed for an additional two minutes to insurehomogeneity. In the case of uncured blends, the compositions were mixedfor 8-10 minutes, dumped, and then remixed for two minutes.

Peroxide cures were effected using commercial Varox 50% active powder.Sulfur cures were obtained using 5 phr (parts per hundred parts rubber)ZnO, X/2 phr methyl tuads, X/4 phr MBTS, and X phr sulfur in the orderstated with 30 second-1 minute intervals between ingredients.

The blends were pressed into 75 mil thick tensile sheets at 425° F.(Nylon 11) or 450° F. (Nylon 6). Dumbells were cut from the tensilesheets and pulled at 2"/minute. Other tests such as oil volume swell,and hardness were run on samples cut from the plaques, according to ASTMprocedures or slight variations thereof. Oil volume swells were carriedout for 72 hours at 212° C. in ASTM #3 oil.

EXAMPLE 2

Table I shows the effect of resin level on properties for uncuredcompositions of the elastomer of Example 1 and a commercial Nylon 11molding resin (Rilsan BMNO). It is noted that increasing the resin levelraises the tensile strength, hardness, and resistance to oil, but lowersthe ultimate elongation.

                  TABLE I                                                         ______________________________________                                        Uncured TPE Compositions                                                                               TS   %     Shore D                                                                              Vol.                               Example                                                                              Resin   Elastomer (psi)                                                                              Elong Hardness                                                                             Swell                              ______________________________________                                        2A     30      70         231 95    --     262                                2B     40      60         580 85    --     150                                2C     50      50         668 45    36     79                                 2D     60      40        1714 30    52     37                                 2E     70      30        2128 20    58     8                                  Nylon  100      0        5291 20    72     .2                                 ______________________________________                                    

EXAMPLE 3

The compositions of Table II include the same rubber and resin as inExample 2. In addition the compositions were dynamically cured using 7parts peroxide per 100 parts rubber. In comparison with the compositionsof Example 2, the addition of the peroxide produces higher tensilestrength and hardness, and lower oil volume swell. The compositions arecompletely thermoplastic and appear on visual inspection to becompletely compatible.

                  TABLE II                                                        ______________________________________                                        Peroxide Cured TPE's                                                                         Properties                                                     Composition (parts)                                                                            TS     Elon-   Shore D                                                                              Vol.                                   Example                                                                              Resin   Elastomer (psi)                                                                              gation                                                                              Hardness                                                                             Swell                              ______________________________________                                        3A     30      70         277 63    27     158                                3B     40      60        1308 125   37     82                                 3C     50      50        1607 60    47     46                                 3D     60      40        2056 30    55     27                                 3E     70      30        2884 33    62      5                                 ______________________________________                                    

EXAMPLE 4

The compositions of Table III include the same rubber and resin ofExample 2. In addition the compositions contained added metal salts at alevel of 5 parts salt per 100 parts rubber. The examples show that theaddition of the metal curing agents improves tensile strength,elongation, and volume swell.

                                      TABLE III                                   __________________________________________________________________________    Metal Cured TPE's                                                                            Metal         Shore D                                                                            Vol.                                        Example                                                                            Resin                                                                             Elastomer                                                                           Agent                                                                              TS(psi)                                                                           % Elong                                                                            Hardness                                                                           Swell                                       __________________________________________________________________________    4A   50  50    none 1034                                                                               75  36   78                                          4B   50  50    Zinc 1523                                                                              100  40   27                                                         Stearate                                                       4C   50  50    ZnO  1705                                                                              100  40   16                                          4D   50  50    MgO  2176                                                                              150  42   15                                          4E   50  50    Calcium                                                                            1441                                                                               90  40   29                                                         Stearate                                                       __________________________________________________________________________

EXAMPLE 5

Table IV lists compositions which demonstrate the added benefit derivedfrom the inclusion of EPDM in the formulation. From 15-50 percent byweight of the ungrafted EPDM may be added to the polyamide thermoplasticcompositions. The nylon and maleic grafted EPM are the same as inExample 2. The ungrafted EPM is an ethylene/propylene copolymer havingan RSV of 2.8 and containing 55 mole percent ethylene. The EPDM is a 2.3RSV terpolymer of ethylene, propylene, and ethylidene norbornene havinga 65:35 molar ratio of ethylene to propylene and containing 8.5 percentby weight ethylidene norbornene. It is reasoned that the compatibilitybetween the ungrafted EPDM and the nylon is provided by the presence ofthe maleic grafted EPM. The added improvements in properties arereasoned to be derived from the higher cross-link density obtained fromEPDM vs. EPM for a given level of curative. EPDM is recognized to befaster curing than EPM because it contains carbon-carbon double bonds.Other hydrocarbon elastomers which cure faster or provide a highercrosslink density than EPM would be expected to provide the samebenefit.

Other features of Table IV that should be noted are as follows. Examples5A, 5F, and 5J serve as controls and demonstrate the fact that poorproperties are obtained in the absence of the amine reactive elastomer,i.e., the grafted EPM. Examples 5 G-I demonstrate that cures whichrequire the presence of, double bonds can be used effectively when EPDMis included. Additionally some improvement in properties is noted withincreasing levels of curatives. It should also be pointed out that theapparent low volume swell for the control 5A is somewhat misleading.Instead of swelling due to absorption of oil, that sample lost weightbecause rubber was extracted by the oil. All of time control samples hada laminated appearance, whereas all of the samples containing aminereactive elastomer were uniform in structure.

                                      TABLE IV                                    __________________________________________________________________________    EPM/EPDM/Nylon TPE's                                                          Composition (parts)       Properties                                                 Grafted                                                                            Ungrafted         %   Shore D                                                                            Vol.                                   Ex.                                                                              Resin                                                                             EPM  EPM   EPDM                                                                              Cure.sup.1,2                                                                      TS(psi)                                                                           Elong                                                                             Hardness                                                                           Swell                                  __________________________________________________________________________    5A 50   0   25    25  none                                                                               665                                                                               25 27   11                                     5B 50  25   0     25  none                                                                               935                                                                               50 43   65                                     5C 50  25   0     25  3P  1881                                                                              125 47   48                                     5D 50  25   0     25  5P  2283                                                                              163 47   43                                     5E 50  25   0     25  10P 2719                                                                              200 49   42                                     5F 50   0   25    25  10P 1610                                                                               35 52   40                                     5G 50  25   0     25  .5S 2341                                                                              200 45   52                                     5H 50  25   0     25  1S  2759                                                                              245 47   53                                     5I 50  25   0     25  2S  2567                                                                              225 45   47                                     5J 50   0   25    25  2S   858                                                                               50 42   68                                     __________________________________________________________________________     .sup.1 XP = parts Varox powder (40% active on clay) per 100 parts rubber      (phr).                                                                        .sup.2 XS = 5 phr ZnO, X/2 phr methyl tuads, X/4 phr MBTS, X phr sulfur       added in the order stated.                                               

EXAMPLE 6

Table V demonstrates the effect of resin level on properties forcompositions of the type described in Example 5. Again it is seen thatincreasing resin levels result in higher tensile strength, higherhardness and better resistance to oil.

                                      TABLE V                                     __________________________________________________________________________    Effect of Resin Level on Properties of                                        EPM/EPDM/Nylon TPE's                                                          Composition (parts)                                                                    Grafted          %   Shore D                                                                            Vol.                                       Examples                                                                           Resin                                                                             EPM  EPDM                                                                              Cure.sup.(1)                                                                      TS(psi)                                                                           Elong                                                                             Hardness                                                                           Swell                                      __________________________________________________________________________    6A   30  35   35  none                                                                               323                                                                              125 22   256                                        6B   40  30   30  none                                                                               490                                                                              100 30   141                                        6C   50  25   25  none                                                                               935                                                                               50 43   65                                         6D   60  20   20  none                                                                              1822                                                                               35 55   30                                         6E   70  15   15  none                                                                              2671                                                                               25 62    8                                         6F   30  35   35  10P 1118                                                                              120 32   90                                         6G   40  30   30  10P 2230                                                                              175 42   59                                         6H   50  25   25  10P 2719                                                                              200 49   42                                         6I   60  20   20  10P 3497                                                                              225 60   17                                         6J   70  15   15  10P 4140                                                                              250 65    4                                         6K   30  35   35  2S   984                                                                              175 32   112                                        6L   40  30   30  2S  1889                                                                              190 38   78                                         6M   50  25   25  2S  2567                                                                              225 45   47                                         6N   60  20   20  2S  3215                                                                              250 57   26                                         6O   70  15   15  2S  3451                                                                              225 62    5                                         __________________________________________________________________________     .sup.(1) As in Table IV.                                                 

EXAMPLE 7

Table VI describes compositions based upon the elastomer of Example 1(Grafted EPM), an EPDM having an RSV of 2.8 with an ethylene:propyleneratio of 65:35, also with an ethylidene norbornene content of 4 weightpercent, and a commercial Nylon 6 molding resin (Capron 8202C, AlliedPlastics).

                                      TABLE VI                                    __________________________________________________________________________    EPM/EPDM/Nylon 6 TPE                                                                               Properties                                               Composition (parts)          TS   Shore A                                     Example                                                                            Resin                                                                             Grafted EPM                                                                           EPDM                                                                              Cure.sup.(1)                                                                      (psi)                                                                             % Elong                                                                            Hardness                                    __________________________________________________________________________    7A   35  35      30  none                                                                               236                                                                               50  72A                                         7B   35  35      30  2S  1132                                                                              200  75A                                         __________________________________________________________________________     .sup.(1) As in Table IV.                                                 

EXAMPLE 8

Table VII illustrates the effect of a nylon plasticizer on thecomposition properties. The rubber and resin are those of Example 6. Theplasticizer is nonyl phenol.

                                      TABLE VII                                   __________________________________________________________________________    Effect of Plasticizer                                                         Compositions (parts)      Properties                                                   Grafted  Nonyl       %   Shore D                                     Example                                                                            Resin                                                                             EPM  EPDM                                                                              Phenol                                                                            Cure.sup.(1)                                                                      TS(psi)                                                                           Elong                                                                             Hardness                                    __________________________________________________________________________    8A   50  25   25   0  5P  2719                                                                              200 49                                          8B   40  20   20  20  5P  1925                                                                              300 40                                          __________________________________________________________________________     .sup.(1) As in Table IV.                                                 

It will be apparent from the foregoing that marked improvement intensile strength and elongation can be achieved, in accordance with thepractice of the invention, by blends that are formed of polyamide resinsand functionalized elastomeric materials and in which the dispersedelastomeric materials have been cross-linked. It will be understood thatadditional improvement in the properties may be obtained through theaddition of a non-functionalized faster curing elastomeric materialprior to cross-linking of the dispersed elastomeric material. It will beunderstood further that changes may be made in the details offormulation and operation without departing from the spirit of theinvention, especially as defined by the following claims.

What is claimed is:
 1. A polyamide thermoplastic elastomer blend havingimproved tensile strength and elongation properties comprising:(a) atleast 30 percent by weight of a EPM or EPDM rubber which has beenmodified by having grafted thereto an anhydride having the formula:##STR3## or the corresponding unsaturated dicarboxylic acid or mixedacid/ester having the formula: ##STR4## in which R is an alkylene groupcontaining 0-4 carbon atoms, Y is selected from the group consisting ofhydrogen, halogen and an organic group having from 1-12 carbon atoms,and X is a hydroxyl, alkoxy or aryloxy group and at least one X ishydroxyl, (b) at least 10 percent by weight of a polyamide resin and,(c) 15-50 percent by weight of an unmodified hydrocarbon elastomer, inwhich said rubber (a) and elastomer (c) after dispersion in saidpolyamide resin are cross-linked by a cross-linking agent selected fromthe group consisting of peroxides, metal stearates, metal oxides,phenolic resin and sulfur.
 2. The polyamide thermoplastic elastomerblend according to claim 1 further comprising at least one modiferselected from the group consisting of flame retardants, stabilizers,fillers, plasticizers and oils.
 3. A method of producing polyamideelastomer blends having improved tensile strength and elongationproperties comprising the steps of dispersing (a) from at least 30percent by weight of an EPM or EPDM rubber which has been chemicallymodified by having grafted thereto an anhydride having the formula:##STR5## or the corresponding unsaturated dicarboxylic acid or mixedacid/ester having the formula: ##STR6## in which R is an alkylene groupcontaining 0-4 carbon atoms, Y is selected from the group consisting ofhydrogen, halogen and an organic group having from 1-12 carbon atoms,and X is a hydroxyl, alkoxy or aryloxy group and at least one X ishydroxyl, and (b) from 15-50 percent by weight of an unmodifiedhydrocarbon elastomer into (c) at least 10 percent by weight of apolyamide resin, and cross-linking said rubber (a) and elastomer (b)after dispersion in the polyamide resin by means of a cross-linkingagent selected from the group consisting of peroxides, metal stearates,metal oxides, phenolic resin and sulfur.
 4. The method according toclaim 1 in which the polyamide thermoplastic elastomer blend is formedby reaction of the components in melt processing equipment.
 5. Themethod according to claim 4 in which the components are reacted in meltprocessing equipment selected from the group consisting of an extruder,brabender plasticorder and banbury mixer.
 6. The method according toclaim 3 further comprising the addition of at least one modifierselected from the group consisting of flame retardant, stabilizers,fillers, plasticizers and oils.